Scroll-type displacement machines are commonly employed as a compressor for various gases, including air and refrigerants. However, they are readily adapted for use as a compressed vapor expander (e.g. pneumatic motor), a liquid pump, or a hydraulic motor. In normal operation, scroll-type machines have high pressure in the center region of the scroll pair and low pressure around the outside periphery. Fluid flows from the outside to the inside for compressors and pumps and from the inside to the outside for expanders and motors.
In the case of so-called low-side machines, where the housing containing the scroll mechanism contains working fluid at the low-pressure level, means are provided to isolate the high pressure fluid passing through the high pressure port in the fixed scroll, sometimes through a simple discharge tube attached to the fixed scroll and more commonly through a high pressure manifold or pulse volume integrated into the external housing and further communicating externally through a high-pressure tube or fitting.
For so-called high-side machines the low-pressure flow is connected directly to the scroll pair at the periphery and the high-pressure flow exits at the center of the scroll pair and passes through an external housing which contains the pressurized flow. The high pressure flow serves to cool the bearings and any other heat-generating components such as motors or sliding mechanisms. The orbiting scroll typically has a drive bearing located at the center of the scroll on the opposite side from the spiral vanes. In order to isolate this drive system from the direct fluid flow, the high pressure port is typically located at the center of the fixed scroll, on the opposite side of the scroll set from the drive bearing. The high-pressure port in the fixed scroll communicates directly with the interior of the external housing. In such an arrangement means are provided for flow to pass around the scroll set to communicate between the discharge port on one side of the scroll set and the rest of the external housing on the other side. This may take the form of an enlarged external housing or special gas passage means to carry the fluid. These options represent some degree of increased size and weight for the overall compressor assembly along with associated complications in manufacture.
Accordingly, an aspect of the invention is directed towards improvements over the state of the art as it relates to routing high pressure fluid in a high-side machine to avoid the disadvantages associated with conducting high pressure working fluid between a fixed scroll high pressure port and the external compressor housing.
In all these configurations a drive shaft, used either to input or to extract mechanical power, is provided with support bearing means to support radial loads and to allow free rotation of the drive shaft. Interposed between the drive shaft and the orbiting scroll is an eccentric drive bearing which may take the form of an eccentric bearing, a so-called slider block, or an eccentric bushing, all serving to provide an eccentric drive to connect between the drive shaft and the orbiting scroll and to drive the orbiting scroll in a circular path, i.e., a circular non-rotating orbit. The eccentric drive bearing may take the form of a bearing rigidly attached to the drive shaft and which drives the orbiting scroll through a fixed orbital radius or it may take the form of a so-called radially compliant drive where the radial position of the orbiting scroll relative to the drive shaft center is permitted to vary in response to misalignment and tolerance variations so as to maintain positive contact at all times between the vane walls of the orbiting scroll and the fixed scroll.
Additionally, a counterweight arrangement is provided to achieve a dynamic balance among the various orbiting, rotating, and translating masses within the machine. Typically, a primary counterweight nearest the orbiting scroll provides a static balance for the machine. However, the axial spacing between the planes of unbalance of the moving components and the plane of action of the primary counterweight results in an overturning moment which tends to impose a wobbling-type load onto the shaft and consequently onto compressor frame which results in undesirable vibration. To counteract this dynamic unbalance, a secondary counterweight is provided toward the end of the shaft opposite the orbiting scroll (on the other side of said primary counterweight) to create a counteracting overturning moment. An equivalent mass unbalance may also be added to the primary counterweight to maintain static balance. In a way, the scroll-type machine may be said to have three counterweights: one larger counterweight to provide a static balance and two smaller counterweights of identical unbalance phased 180 degrees from each other and axially separated to provide a dynamic balance with one of the smaller counterweights at the same location as the larger counterweight. The primary counterweight may thus consist of the combination of the larger counterweight and one of the smaller counterweights while the secondary counterweight is simply the other smaller counterweight.
The offset between the drive shaft center and the center of said eccentric drive bearing defines an angular reference which rotationally orients the drive shaft. The moving masses within the machine may all be defined by their axial position along the axis of the drive shaft and by their angular orientation relative to the eccentric drive bearing angular reference. Likewise, the locations of the primary counterweight and the secondary counterweight are also defined by axial positions along the drive shaft axis and their angular positions relative to the eccentric drive bearing angular reference. The mass unbalances of these counterweights are chosen to counter the mass unbalances of all the moving masses.
In typical scroll machines, the drive means, the primary counterweight, and the secondary counterweight are all separate components located at separate axial locations along the drive shaft. Typically the primary counterweight is interposed between the support bearing and the drive means and said secondary counterweight is placed at the opposite end of the drive shaft. During manufacture, locating means must be provided to position these counterweights properly both axially and angularly onto the drive shaft. Such locating means may consist of locating features between the counterweights and the drive shaft, they may consist of external fixturing, or they may consist of a combination of locating features and fixturing. This construction requires fabrication, alignment, and assembly of a number of components during manufacture of the scroll machine, all of which adds to the cost of manufacture. In some designs, the drive shaft and primary counterweight may be combined into a single component but with the same general overall layout.
The support bearing means typically includes two bearings supporting the main drive shaft which are in turn supported by a structure, frame or shell. In scroll-type machines where a motor (for compressors or pumps) or a power transfer device (e.g. a generator for expanders or hydraulic motors) is integrated into the scroll-type machine, the motor or power transfer device is supported by the structure or frame and is located between the two bearings or just outboard of the two bearings. The rotor component of the motor or power transfer device is affixed onto the drive-shaft. The result of such close integration is that drive shaft, counterweights, and structure or frame are to a large extent custom designed for a single motor or power transfer device. This has advantages in reducing material content in high volume production of larger machinery but is relatively inflexible or difficult to change if variations in the design of motor or power transfer device are desired.
One requirement for proper operation for scroll-type machines is that the two scrolls must be constrained from any relative rotation between them. The orbiting scroll follows a circular path or orbit with respect to the fixed scroll but relative rotation is not permitted. In some designs, both scrolls are adapted to rotate together on offset axes (as opposed to the conventional fixed-orbiting arrangement) but they both rotate at the same speed and the angular phasing between the two scrolls remains the same, which is to say they do not rotate relative to one another.
Several different mechanisms may be used to prevent the relative rotation between the two scrolls, but an Oldham coupling (comprising an Oldham ring and mating features on the two respective scrolls) is in common use today. A typical Oldham ring comprises a solid body, more or less ring-shaped. The body may be an oblong or irregular shape to fit around other features in the machine but it will generally follow the pattern of a closed ring. Axial or radial projections from the Oldham ring body are provided with axially extending surfaces or keyways which engage matching surfaces on the respective scrolls to complete the coupling assembly and to prevent relative rotation between the scrolls while permitting orbiting action.
The ring-shaped portion of the Oldham ring is typically flat and of a more or less uniform thickness, being generally distributed about a radial plane at all points around the ring. A radial plane which passes through the centroid of the Oldham ring will divide the Oldham ring into two continuous ring-shaped portions. Thus the main body of the Oldham ring will have a space set aside specifically to contain it and allow free motion during operation. This dedicated space adds to the overall height (i.e. axial length) of the scroll-type machine and thereby increases the size and weight of the scroll machine.
Thus an aspect of this invention is directed towards improvements over the state of the art as it relates to the design of an Oldham coupling to avoid the need for a dedicated axial space for the coupling and thereby to reduce the overall size of the displacement machine.
In some applications where the working fluid (vapor) must be isolated from the outside air (such as in a refrigeration circuit) the compressor and drive motor are contained within a sealed housing which isolates the working fluid from the outside environment. The vapor flows around the compressor and motor and provides cooling, especially for the motor.
The drive motor, typically an electric motor, is normally integrated into the overall compressor assembly. The motor stator is integrated into the compressor frame and the motor rotor is mounted directly onto the compressor shaft, which also incorporates the compressor drive means (e.g. eccentric bearing) and counterweights which may be placed on both sides of the motor or even attached directly to the rotor. This arrangement provides acceptable economy and simplicity by minimizing the number of separate components that make up the motor and compressor combination. However, a given compressor is then dedicated to a particular motor size and design. Physical changes to the motor often require extensive changes to the compressor frame and drive shaft to accommodate the new motor.
In larger compressors the motor lineup is typically standardized with common motor sizes and configurations found across a relatively limited selection of motor suppliers. There is seldom a need to change to a different size motor and the compressor design can be relatively stable with regard to motor selection.
But in smaller compressors, there is a very wide variety of motor types and manufacturers to choose from. These motors are normally available as prepackaged modules with motor housing, shaft, and bearings integrated together into a single product intended for a wide array of applications, a small scroll compressor being only one of them.
So another aspect of this invention is directed towards a general compressor design which allows use of a range of prepackaged motors of various sizes with minimal if any changes to the compressor or to the motor.